Grip bolt



Feb. 17, 1942. H. A. HARRIS r-:rAL 2,273,102

GRIP BOLT Filed Feb. 14, 1941 l mwww/ M/ FOP THE F IKM A Tree/vf: Ks.

Patented Feb. 1 7, 1942 UNITED STATES ATENT OFFICE GRIP BOLT Harry A.Harris, Whittier, and David Rasky, Los Angeles, Calif.

Application February 14, 1941, Serial No. 378,856

1 Claim.

Our invention relates to machine elements, and the principal object isto provide means by which a primary member can be locked againstmovement with relation to a secondary member. Our invention has apeculiar utility when applied to scientific instruments, and althoughitmay be used for many other purposes, and we do not intend to limit ourinvention to this particular use, We will conne our description to thisparticular use. It is a further object of our invention to provide adevice for rmly locking such primary and secondary members together insuch a manner that the surfaces of these members which are in contactwith each other will not be marred or scratched.

Referring to the drawing, which is for illustrative purposes:

Fig. 1 is a side elevation of a locking device;

Fig. 2 is an end elevation of same;

Fig. 3 is a section showing one application of the device;

Fig. 4 is a section on a line 4-4 of Fig. 3; and

Figs. 5 and 6 are enlarged sections o-f a por tion of Fig. 3.

The method of using our invention can be understood from an inspectionof Fig. 3, in which II is a cylindrical primary member which slides orturns in a cylindrical bore in a secondary member I2. The primary memberII is very accurately fitted in this bore so that if its exteriorsurface is scratched, it will not turn or slide freely. Suchconstructions are used in various types of scientific instruments, theparts of which must at all times be accurately aligned with each other.

To provide a device which will enable the primary member II to berigidly locked in the secondary member I2, we provide a grip bolt I3which has a threaded portion I4 and which may have any sort of a head orshank I5 by which the bolt I3 may be turned. The end I6 of the grip boltI3 has a counterbore II in which is placed a conical or cylindricalmember I8 formed of a material softer than the primary member I I, softvulcanized rubber being an excellent material to use. The member I8 mayhave a head I9 slightly smaller than the diameter of the threadedportion I4 of the grip bolt I3 at the base of the threads thereof. Thegrip bolt is threaded in the secondary member I2 and the end I6 isslotted as shown at 2|.

The method by which the grip bolt I3 grips the primary member II will beunderstood from a study of Figs. 5 and 6. As the grip bolt is turned, itis forced to the right, as seen in Fig. 3, so that the end I6 is forcedtoward the secondary member I2.

plane represented by The head I9 of the member I3 is thus forced againstthe member II and is deformed in shape, the head I9 becoming of largerdiameter as the bolt is screwed home. If the bolt is turned further thehead I9 substantially lls the cavity 22 between the end I6 of the boltI3 and the member II. Rubber and, in fact, most soft materials, beingonly slightly compressible although freely deformable, may also be used.As soon as the head I9 of the member I8 entirely lls the cavity 22, avery high internal pressure may be developed in the body of the rubberwhich causes the rubber to adhere to the outer surface of the member IIand to conform to the cylindrical contour of that surface. This` highinternal pressure on the soft material is transmitted to the softmaterial in the counterbore I'I, and this pressure, being exertedoutwardly, tends to expand the bolt against the threads of the member I2and thus causes the bolt to be frictionally locked against turning. Theend I6 of the bolt, being provided with the slot 2l, can be readilyexpanded sufficiently to provide this locking.

Since the material from which the member I8 is made is considerablysofter than the material used in the member II, no amount of pressureexerted by the member I8 on the member II will injure the surface of themember II and, even after it has been subjected to such pressure, if thepressure is released by backing oi the bolt I3, the member II can stillslide andv turn freely in the member I2.

We claim as our invention:

A device for insuring the rigid locking of a primary member to or in asecondary member in such manner that said members, at any time, can bereleased from rigid relationship with each other, and the contactbetween the surfaces of said members will not be'impaired due to saidlocking, comprising: a bolt threaded in said secondary member in such amanner that it may be advanced toward or retracted from the surface ofsaid primary member by a rotation of said bolt; and a body of materialsofter than the material of said primary member, said material beingcarried in a cavity in the end of said bolt adjacent said surface, saidmaterial projecting beyond the end of said bolt in the form of anenlarged head smaller in diameter than the body of said bolt, so that,as said bolt is advanced toward said surface, said projecting endfrictionally contacts said surface and is compressed between the end ofsaid bolt and said surface.

HARRY A. HARRIS. DAVID RASKY.

